Chemical sensors, particularly biosensors operating with bioactive components, are based on microporous (e.g., pore diameter <20 Å) and mesoporous (e.g., pore diameter 20 Å to 500 Å) materials such as, for example, SnO2 or WO3 films. The chemical structure of such materials permits guest molecules to access large internal void surfaces and cavities, and thereby enhance the catalytic activity and adsorptive capacity of these materials. Examples of microporous materials are aluminosilicate molecular sieves, also known as “zeolites”. In zeolites, the micropores form regular arrays of uniformly-sized channels and can function as a host to ionic and neutral molecular guest species. The utility of sensors and devices fabricated from zeolites and other microporous materials, however, is generally limited to those applications where the guest or analyte molecules have sufficiently small kinetic diameters to pass through the narrow microporous void openings.
Mesoporous materials offer the advantage of larger pore sizes, making them compatible with applications such as those involving the separation or sensing of relatively large organic molecules. Mesoporous materials are amorphous or polycrystalline solids such as pillared clays and silicates. Unfortunately, the pores in such materials are often irregularly spaced and broadly distributed in size, making them ill-suited for chemical separations, sensing, and other device-oriented applications. Such microporous and mesoporous materials have very high specific areas. Because the pores are irregular and usually less than 50 nm (or even less than 20 nm), however, the fluent resistance of the sensing material is high and some internal surface is not applicable. Also, such materials are relatively difficult to clean after each usage and the residue of a previous sample can affect new measurements, which are depicted graphically as a floating of the baseline of the sensor.
Based on the foregoing, it is believed that a need exists for an improved three-dimensionally ordered macroporous (3DOM) sensor apparatus. A need also exists for an improved method for fabricating such a 3DOM sensor apparatus, as described in greater detail herein.